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Guide · Disk repair

How to repair your Mac’s startup disk with First Aid in Recovery

By the AI Repair team · Updated

Your Mac can’t repair the disk it is running from: macOS won’t let it. So you start your Mac in Recovery, a part of macOS kept apart for repairs, and run First Aid from there. While you do, your Mac’s screen can’t show this page, so open it on your phone or another device before you begin. The steps below are short, to follow on a small screen.

In short

Back up first if you can. Shut down your Mac, then start it in Recovery: on a Mac with Apple silicon, press and hold the power button until you see Options; on an Intel Mac, press the power button, then hold ⌘ and R. Choose Disk Utility, then View › Show All Devices. Run First Aid (never Erase, which deletes everything) on the last item under your Mac’s disk, then on each item above it, up to the top. Then restart.

Before you start

  • Find out which Mac you have. Choose Apple menu › About This Mac. If it shows Chip, such as Apple M1, your Mac has Apple silicon. If it shows Processor, with Intel in its name, it’s an Intel Mac (Apple’s guide).
  • Back up with Time Machine, or copy your important files to another drive, while your Mac still lets you. A repair can lose files that are badly damaged.
  • Know a password. Recovery may ask you to choose a user and type its password. Choose a user you know the password for. If yours isn’t listed, use the account of the person who set up this Mac.
  • Plug in a MacBook, and keep this page open on your phone. If your Mac is on Wi-Fi, have its password handy too.

Start in Recovery: a Mac with Apple silicon

If your Mac won’t shut down in step 1, press and hold the power button for up to 10 seconds, until it turns off (Apple’s steps for Recovery).

  1. Save your work. Click the Apple menu at the top left, choose Shut Down, then click Shut Down. Wait until the screen is black.
  2. Press and hold the power button (on a laptop, the Touch ID button). Let go when you see “Loading startup options” or Options.
  3. Click Options, then Continue. If asked, choose your Mac’s disk (usually Macintosh HD) and click Next.
  4. If asked for a user, choose one you know the password for, click Next, type the password and click Continue.
  5. Choose Disk Utility, then click Continue. Then follow the First Aid steps.

Start in Recovery: an Intel Mac

If your Mac won’t shut down in step 1, press and hold the power button for up to 10 seconds, until it turns off (Apple’s steps for Recovery).

  1. Save your work. Click the Apple menu at the top left, choose Shut Down, then click Shut Down. Wait until the screen is black.
  2. Press the power button, then at once press and hold Command (⌘) and R until you see an Apple logo or a spinning globe.
  3. If asked, choose your Wi-Fi network. If asked, choose your Mac’s disk (usually Macintosh HD) and click Next.
  4. If asked for a user, choose one you know the password for, click Next, type the password and click Continue.
  5. Choose Disk Utility, then click Continue. Then follow the First Aid steps.

A spinning globe means your Mac is loading Recovery over the internet, so it needs a connection: choose your Wi-Fi network when asked, or plug in a network cable.

Run First Aid

In Disk Utility, First Aid checks each part of the disk and repairs what it can. It starts with the last item and works up to the disk itself (Apple’s steps for First Aid):

Click First Aid, never Erase. Erase deletes everything on the disk, and both buttons are in the row at the top of Disk Utility.

  1. In Disk Utility, choose View › Show All Devices.
  2. In the list on the left, under Internal, click any arrow (>) to show what is inside. Then click the last item.
  3. Click First Aid (not Erase), then Run. If asked for a password to unlock the disk, type the one you log in with.
  4. When it finishes, click Done. Then run First Aid on each item above it, up to the top. Skip an item whose First Aid is grey.
  5. When First Aid has finished, click the Apple menu and choose Restart.

On most Macs the last item is Macintosh HD - Data and the top one is the disk itself, though the names on yours may differ; Apple says to check both Macintosh HD and Macintosh HD - Data. Let each check finish before you click anything else: on a big disk it can take a while.

What First Aid’s result means

  • It says the disk is OK, or that it repaired it. Restart, and you’re done.
  • It reports “overlapped extent allocation” errors. Two or more files were using the same space on the disk, and at least one of them is likely damaged. Disk Utility lists them in a DamagedFiles folder at the top of the disk: delete the ones you can replace, and open the others to check them (Apple’s guide).
  • It found errors it couldn’t repair. Run First Aid once more. If it still fails, back up everything you can, then erasing the disk and reinstalling macOS is Apple’s next step. That deletes everything on the disk, so a repair shop or Apple Support can help if you’d rather not do it yourself.
  • It says the disk is about to fail. No repair fixes that. Back up your files now, and have the disk or the Mac seen by Apple or a repair shop.

To leave Recovery at any time, choose Apple menu › Restart or Shut Down.

A drive plugged into your Mac

An external disk, a USB stick or a memory card doesn’t need Recovery: you can run First Aid on it while your Mac is running. A repair can’t be undone, and badly damaged files may be lost. Copy what matters first if you can.

  1. Save and close any files on the drive, and quit apps that use it.
  2. Click the Finder (the smiling face) in the Dock. Choose Go › Utilities at the top, then double-click Disk Utility.
  3. In Disk Utility, choose View › Show All Devices.
  4. In the list on the left, under External, find your drive and click the last item under it.
  5. Click First Aid (not Erase), then Run. When it finishes, click Done, and run First Aid on each item above it, up to the drive itself.

For a memory card, step 4 is different. In the list on the left, find your card under External (or under Internal, for the Mac’s own card slot) and click the last item under it.

If your Mac says it can’t read a drive you’ve just plugged in, click Ignore, never Initialize, which erases it. Then run First Aid on it as above.

Advice you can skip

  • Typing fsck commands in Terminal or single-user mode. It’s old advice: Apple turned off single-user mode in macOS Mojave, and First Aid does the same job with fewer ways to go wrong.
  • Erasing the disk at the first error. Run First Aid first. Erasing deletes everything, so keep it for a disk First Aid can’t repair, after a backup.
  • Repairing the startup disk while your Mac runs from it. macOS refuses, which is why Recovery exists.
  • Buying a disk repair app before you’ve tried First Aid. It comes with every Mac and is Apple’s own tool for this.

Common questions

Is it safe to run First Aid on my Mac?

Yes. It’s Apple’s own tool, and it checks and repairs the disk’s structure without erasing your files. Apple still asks you to have a backup first, because a disk with errors can have files that are already damaged, and a repair can’t always save them.

Why can’t I repair my startup disk while my Mac is running?

Because macOS is using it. A repair needs the disk to itself, so Disk Utility can only check the startup disk while your Mac runs from it. Recovery starts your Mac from a separate part of macOS, where First Aid can repair the disk.

How long does First Aid take?

It depends on the size of the disk and how much is on it: often a few minutes on a Mac with an SSD, longer on a large hard disk. Let it finish, and don’t turn your Mac off while it runs.

What if First Aid can’t repair my Mac’s disk?

Run it once more. If it still fails, back up what you can; Apple’s next step is to erase the disk and reinstall macOS, which deletes everything on it. If Disk Utility says the disk is about to fail, back up and have it replaced instead.

How do I get out of Recovery on a Mac?

Choose Restart or Shut Down from the Apple menu. Your Mac then starts up from its disk as usual.